The present invention relates to a system for switching lines when a failure occurs on a communication line of a network system and in particular to a line switching system for switching communication lines under a remote and centralized control of a network control center.
In a network system which couples computers at remote places for mutual communications, reliability of the network system is regarded as important. Counter-measures such as duplexing of units and switching of a faulty line to a backup line when a failure occurs have been taken.
JP-A-2-60337 discloses a line switching technique when a failure occurs on a communication line in a network system in which a plurality of computers are connected with each other via line switching units, communication lines and backup lines, and a network control center is connected with the line switching units. When the failure occurs, a line switching instruction is issued from the remote network control center to each of the line switching units. The line switching units which receive the instruction switch the faulty communication line to a backup line.
The above mentioned JP-A-2-60337 does not teach a method for estimating and displaying the location of failure and a scheme of the operation performed by the network control unit in the network control center in a network system in which a plurality of computers are connected with each other via line switching units, communication lines and backup lines and the network control unit is thereby connected with the line switching units, as mentioned above.